HARTFORD - New England’s air quality improved this summer compared with last year because of fewer sweltering days, the Environmental Protection Agency said yesterday.
Between April and September, the six-state region had 16 days when ozone levels were considered unhealthy, according to preliminary data from the EPA. That is down from 29 unhealthy days in 2010.
This year’s air quality improvement is directly related to the decrease in the number of hot days, the EPA said. At Bradley Airport near Hartford, the temperature reached at least 90 degrees on 15 days this year; there were 34 days with 90-degree temperatures in 2010.
But over the long term, stricter vehicle emission standards have resulted in cleaner air, EPA officials said. New England has had a steady decline in the number of smoggy days over the past three decades.
“We can all feel proud and breathe easier, thanks to the progress we have made in reducing air pollution,’’ EPA regional administrator Curt Spalding said in a statement.
Connecticut this year had 14 unhealthy days, compared with 24 last year. Massachusetts had 10 unhealthy days, down from 14. Rhode Island had six, the same as last year, and Maine had three, down from eight.
New Hampshire had two unhealthy days, down from eight. Vermont, which had none last year, was the only state with an increase, logging one unhealthy day this year.
This year’s number of unhealthy days is the second-lowest since 1983, when New England had 113 unhealthy days. The lowest figure was in 2009, when ozone concentrations reached unhealthy levels on 11 days.
Cars, trucks, and other vehicles emit most of the pollution that causes smog, but power plants that use fossil fuels can also give off substantial amounts, the EPA said. Gas stations, gasoline-powered lawn equipment, print shops, and household products like paints and cleaners also contribute to the problem.